How to send mail in c using tls

To send mail using TLS (Transport Layer Security) in C, you can use the following steps:

Step 1: Install the necessary libraries

You'll need to install the following libraries:

OpenSSL (for TLS encryption)
libcurl (for sending the email)

On Ubuntu-based systems, you can install them using:

sudo apt-get install libssl-dev libcurl4-openssl-dev

On macOS (with Homebrew), you can install them using:

brew install openssl curl

Step 2: Set up the email server

You'll need to set up an email server that supports TLS. You can use a local email server like Postfix or a cloud-based email service like Gmail.

For example, if you're using Gmail, you'll need to enable IMAP and SMTP access in your account settings.

Step 3: Write the C code

Here's an example C code that sends an email using TLS:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

#define SMTP_SERVER "smtp.gmail.com"
#define SMTP_PORT 587
#define FROM_EMAIL "[email protected]"
#define TO_EMAIL "[email protected]"
#define SUBJECT "Test email from C"
#define MESSAGE "This is a test email sent from C using TLS."

int main() {
    CURL *curl;
    CURLcode res;
    SSL_CTX *ssl_ctx;
    SSL *ssl;
    BIO *bio;

    // Initialize OpenSSL
    SSL_library_init();
    SSL_load_error_strings();

    // Create a new SSL context
    ssl_ctx = SSL_CTX_new(TLS_client_method());
    if (!ssl_ctx) {
        fprintf(stderr, "Error creating SSL context\n");
        return 1;
    }

    // Load the SSL certificate
    SSL_CTX_load_verify_locations(ssl_ctx, NULL, NULL);

    // Create a new SSL object
    ssl = SSL_new(ssl_ctx);
    if (!ssl) {
        fprintf(stderr, "Error creating SSL object\n");
        return 1;
    }

    // Set the SSL object's certificate
    SSL_set_fd(ssl, -1);

    // Create a new BIO object
    bio = BIO_new_socket(-1, BIO_NOCLOSE);
    SSL_set_bio(ssl, bio, bio);

    // Set up the SMTP connection
    curl = curl_easy_init();
    if (!curl) {
        fprintf(stderr, "Error initializing curl\n");
        return 1;
    }

    curl_easy_setopt(curl, CURLOPT_URL, "smtp://smtp.gmail.com:587");
    curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);
    curl_easy_setopt(curl, CURLOPT_SSL_CTX, ssl_ctx);
    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_EMAIL);
    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, TO_EMAIL);
    curl_easy_setopt(curl, CURLOPT_READDATA, MESSAGE);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);

    // Send the email
    res = curl_easy_perform(curl);
    if (res!= CURLE_OK) {
        fprintf(stderr, "Error sending email: %s\n", curl_easy_strerror(res));
        return 1;
    }

    // Clean up
    curl_easy_cleanup(curl);
    SSL_free(ssl);
    SSL_CTX_free(ssl_ctx);
    BIO_free(bio);

    return 0;
}

Step 4: Compile and run the code

Compile the code using:

gcc -o send_email send_email.c -lcurl -lssl -lcrypto

Run the code using:

./send_email

This code sends an email using TLS to the specified recipient. Make sure to replace the placeholders with your own email credentials and settings.

Note: This is just a basic example, and you may need to modify the code to suit your specific requirements. Additionally, you should ensure that your email server is configured to allow TLS connections and that your email credentials are valid.

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How to send mail in c using tls